问题
I'm looking for a way to detect the disconnection of a Bluetooth device immediately after it has happened (2 second max), typically in a "device too far" scenario or Device battery is dead. Currently I can detect it with a BroadcastReceiver by getting a BluetoothDevice.ACTION_ACL_DISCONNECTED, but it takes about 16 to 20 seconds to fire.
- Is there any way to get notified in 2 seconds Max.
- I used BroadcatReceiver but it is not fast enough to get alert in 2 seconds Max, so is there any other kind of approach available to get notification quickly that bluetooth is disconnected.
- I use this createRfcommSocketToServiceRecord(UUID); to connect a paired device and i am bound to use it using UUID.
I have visited a lot of links regarding this issue, but no one matches with my needs.that's why any help would be appreciated.
thanks.
回答1:
I think the only way you can reliably sense loss of connection quickly (within two seconds) is via your own application protocol that you use over the Bluetooth connection. For example, your application protocol might implement a heartbeat that occurs every 500ms. If you don't see a heartbeat within two seconds then you could trigger your own event.
Bluetooth is a socket-based stream protocol that is designed to work over an unreliable medium (i.e. radio), and as such has to tolerate errors in (or loss of) packets. For this reason it will take significantly more than 2 seconds before your Bluetooth stack declares it has given up and disconnected the device, as you have found.
I have an application on Play which is designed to talk with an automotive ECU via Bluetooth and my strategy for sensing disconnection is exactly as I suggested in my first paragraph.
Update 20th June 14
I see in your bounty comment and also your comment below that you're asking for a code example, but it's kind of difficult for me to provide one without knowing anything about the application protocol that you're running over the socket connection. Or to put it another way, what exactly is it about my first paragraph (i.e. the heartbeat suggestion) that you do not understand or cannot create code for yourself? The concept of using a heartbeat really is quite simple. You would define a certain message type in your application protocol that represents a heartbeat message. One end of the connection sends this heartbeat message periodically, say every one second. The other end of the connection checks that this heartbeat message is received every second or so and drops the connection after a two-second time-out. It is impossible to be any more specific than that, because I can't see your existing code and I don't know what kind of messages you are currently exchanging over the socket.
回答2:
After nothing work around! I got two things to get my work done.
I need to check that is my Bluetooth socket is not in use(Sending Receiving) till 2 to 5 sec I disconnect that and when user wants to send data to the receiver device I connect that again.
Or I'll try to connect the socket after 2 to 5 sec so that if it is not ready to connect means it is already connected, else it will be connected and I refresh the previous socket references.
but first option is more valuable to work perfectly in my problem.
回答3:
This is a problem with old bluetooth and more hardware than software.
If you want to notice that the connection is broken you need to do polling (a heartbeat), something like "are you alive? are you alive?"... This is bad for battery so... the users will finally uninstall your app.
I recommend you to change to BTLE (bluetooth low energy), devices like Nexus 5 has this. With BTLE you have a proximity profile which can tell you the quality of the signal, so, you can guess the distance (near, far, out of range) and therefore you can also tell if the devices are disconnected.
Another nice point is that if the devices are out of range but one is again in range you could get noticed as well, so this is really nice for apps to open doors by proximity for example.
Check this: https://developer.bluetooth.org/TechnologyOverview/Pages/PXP.aspx
In the other hand Apple has invented the concept of iBeacons, devices that are distance aware, and the good thing is that there is also an implementation of iBeacons for Android: http://developer.radiusnetworks.com/ibeacon/android/
来源：https://stackoverflow.com/questions/22200364/android-detect-bluetooth-disconnect-immediately-max-2-seconds